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00:00
can because it’s coming out attaching on the
lesser tubercle. Okay. Now, we brieflytouched upon the nerve injuries. I’ll just
go back to other nerve injuries you can get.
00:14
Median nerve injury. So the median nerve, as
the name says, it’slike the middle. That’s what we call median.
Imagine a median nerve is injured there, whatdo you think the patient’s clinical presentation
will be? That’s the median nerve. When doyou think if somebody can get a median nerve
injury at this level, what’s the most commonthing?
Fracture.
00:49
Supracondylar fracture, commonly seen in children,
but, of course, you can get in adults.
00:54
But you have supracondylar fracture; the nerve
that is injured is median nerve. Of courseyou can get the radial nerve, ulnar nerve,
in theory, but for the purpose of your exam,they’ll ask you median nerve, supracondylar
fracture. So, let’s say this is a four-year-oldchild. He doesn’t look four, but he’s
four. Supracondylar fracture, what do youthink this hand will be? What are things
he won’t be able to do?Wrist drop? No, no, no, wrist drop is on
the other side,it's on the radial. We’re talking about
median.
01:27
So, unable to extend the wrist.
Flex you mean?Flex the wrist. Okay. I think I’m just
working you towardsa clinical scenario. They won’t give you
that. What is the thing they will give you?What does the patient unable to do if it is
a child? What does a classical thing a childwill be laying if you’re seeing a child
in any --Grasp. The grasp. Okay. Grasp is lost.
It’s calledthe pointing index, the index finger won’t
flex. So if you see a four-year-old childlaying in any, this is a classical median
nerve injury. That’s called the pointingindex sign. Now, in a child, you can’t ask
him to make a fist. So that’s why it isin that position. But in an adult, if they
are laying this, you ask them to make a fist,again, they won’t be able to make a fist
but the hand will try to flex this way.
02:22
That’s called the hand of benediction. So this is
again a median nerve injury.
02:28
So if we have a median nerve injury at that
level, or even slightly lower down, you willsoon get this pointing index or the hand of
benediction. Okay. Now, let’s go to theanatomy of that. Why do you get this? Going
back to your ulnar nerve, I said these twoare supplied by ulnar nerve, and these two
are by median. So that’s why when you havea median nerve injury, these two don’t flex. But
classically, the middle finger can occasionallybe supplied by the ulnar from there or the
tendon is just pulling it down. But this finger willnever flex. So this is the classical one but
you can get this as well.
03:16
FPL, even this one flex because the FPL is
also by the median nerve. If you come to thecarpal tunnel and you have an injury of the
median nerve at this level, then you won’tget pointing index, you won’t get hand of
benediction, what is lost? Thenar, I meanwasting of thenar, but what does a patient
unable to do?Abduction. Abduction of thumb. So that is
lost in themedian nerve injury. Well, clearly, if it
happens there, it will definitely be lost.
03:50
But if the patient has got a full fist but
unable to just abduct the thumb then it’sthe median nerve lower than the carpal tunnel.
Okay. So these are the levels of median nerveinjury that they will ask you. Ulnar nerve injury.
Ulnar nerve injury, they’ll ask you whetherit can be -- before the epicondyle or after.
If you have an ulnar nerve injury at thislevel, what will you get? What will the patient
sign, acutely and chronically?You get a drop. No, you won’t. In the
chronic situation,you’ll get clawing of the hand. Acutely,
what is the patient unable to do? These twofingers, isn’t it? So if the patient makes
a fist, these won’t flex, these two.
04:51
But with the long standing ulnar nerve injury,
you will get wasting of the hypothenar eminence,claw hand. Now, in your exam, what are the
other things they will expect you to knowabout ulnar nerve in the hand? What are the
functions of ulnar nerve in the hand? Jay-P,what are the other functions of ulnar nerve
in the hand? What are things you can askthe patient to do to check for ulnar nerve
intactness?Flexion of the medial two digits.
Okay. So you can ask them to make a fist,fine, that may be lost, what else? Very good,
spreading the fingers. So that is abductionof the fingers, adduction of the fingers, as well as scissoring.
Then adduction of the thumb and then abductionof the little finger. All of these are for
ulnar nerve injury. So if we have somebodywith an ulnar nerve injury -- so that is lost
in ulnar nerve injury. Then you do the Froment’ssign, which is giving your card between the thumb
and index finger, and then you pull the card out.
06:17
So if the patient has got an ulnar nerve injury,
the adductor pollicis is affected and thepatient will be unable to hold the card but
they will try to hold the card by flexingthe IP joint. Your finger is in that
position. That’s yourpositive Froment’s sign. That’s the
classical of ulnar nerve injury and you’retesting for adductor pollicis. Okay. Back
to you. What’s the mechanism of claw hand?So if it’s a proximal injury, you get a
claw hand and if it’s distally, you don'tbecause you got a compensation. It’s
because if it's a proximal injury, you get --Well, maybe I should just correct you there.
You will get a claw hand in both. Both in highlesion as well as low lesion, you’ll get
a claw hand, but there’s a difference.
07:26
What’s the principle behind the claw hand? What’s
claw hand? Show me how does claw hand look. No.
07:37
How do you distinguish a claw hand from
Dupuytren's contracture or the Volkmann'scontracture? Okay. No, just by looking at
it. In a claw hand, the classical featureis hyperextension of the MCP joint and flexion
of the IP joint.
07:53
So this is claw hand. These two joints have
to be hyperextended. That’s claw hand, becauseif you get this, then you’re getting a number
of conditions. You can get Dupuytren's bonecontracture, Volkmann’s contracture, etc.
But in a claw hand, that’s clawhand. So, that brings us to the muscles in
the hand. To understand claw hand, you needto understand action of muscles. I said this
action, abduction of the fingers. That isby, what interossei? Palmar or dorsal?
Palmar.
08:31
Dorsal, DAB. PAD AND DAB isn’t it? DAB is
dorsal interossei. So dorsal interossei abducts,palmar interossei adducts. So there are four
and four, so eight muscles. Then you havefour hypothenar muscles, four thenar muscles.
So that’s 16, and finally, your lumbricals.
09:02
What is the action of lumbricals? This is
the action of lumbricals. That’s when youput somebody on a plastic cast, you put them in
this position. Because in your normal restingposition of the hand, the lumbricals will
help in flexion of the MCP and extension ofthe interphalangeal joints. That’s the
lumbrical action.
09:23
Now, spread your fingers, that’s all ulnar
nerve, bring it together, all ulnar nerve.
09:40
What about that? Which nerve is this? Radial?
Extension of the --No, this action.
Median and ulnar.
09:50
Very good, yes. So these two are by ulnar
and these two are by median. I will explainthat bit of anatomy now. In the hand, we discuss
about 20 muscles, four thenar, four hypothenar,four palmar interossei, four dorsal interossei,
and four lumbricals. All these are suppliedby the ulnar nerve except those on the radial
site which are called the LOAF muscles.
10:28
So the LOAF is supplied by the median nerve.
L stands for lateral to lumbricals, opponenspollicis, abductor pollicis brevis, and flexor
pollicis brevis. These four are supplied -- well,these four means these five, the lateral two
lumbricals; opponens pollicis, abductor pollicisbrevis, and flexor pollicis. These are supplied
by the median nerve. Everything else is byulnar. So this action, these two are by
median, thesetwo are by ulnar. So, what happens? If you
have an ulnar nerve injury, these two arespared. That’s where you get the clawing.
So what happens in clawing? If you have yourhand in this position, when you have a nerve
injury, the opposite of that happens.
11:19
So, the opposite will be hyperextension of the
MCP and flexion of the interphalangeal joint.
11:27
These two are not affected. It will get clawing
only in those two. This is your claw hand.
11:34
Now, what you said was high lesion and low
lesion. If you have a high ulnar nerve injury,then these two FDPs are also affected on there
because the FDP is supplied by ulnar nervequite higher up here. So your clawing will
be less because they’re also affected.
11:55
The hand is clawed less. But if there’s a low
injury, this nerve is intact, so it'spulling it more. Okay. So that is your
ulnar nerve paradox. If you have a high lesion,the clawing is less. If you have a low lesion
here, the clawing is more. That’s your ulnarnerve injury, ulnar nerve paradox.
So if you got anything related to this inyour EMQs, usually, high lesion, low lesion.
They like high lesion for ulnar nerveand radial nerve because it’s got quite a bit
of clinical significance. Did you understandthe clawing concepts, and the high lesion
and the low lesion? Okay. So that’s allyou need to know about the hand. At this level,
you don’t have to know about the arches.
12:46
You don’t have to know about the pulley
system or the other detailed anatomy. If youwant to ask me anything at this point of what
you’re wasting in other MCQs, if you wantto ask me anything at this point, I can answer
you but I’m not going to any more detailedhigh anatomy because that will be too
much for you.
13:07
Is anybody wanting to know about pulleys?
No, I don’t think so. You need to know whereis the insertion of the FDP and FDS. Where
does the FDP insert, flexor digitorum profundusinsert? Base of the distal phalanx. And FDS?
No, because the FDS has got two strands comingoff. So the FDP and FDS comes here. FDS splits
into two. It’s called the Camper’s chiasm,and it’s attached to the sides of the middle
phalanx. The FDP comes to the middle and attachesto the distal phalanx. That’s your FDP and
FDS insertion.
14:13
Okay. The last bit here is the carpal tunnel,
extremely important. Attachments of the flexorretinaculum. Do you want to say that? Attachment,
yup. Anyone, attachments of the flexor retinaculum.
14:31
Scaphoid? Scaphoid, on the radial
side, okay.
14:40
Trapezium. Trapezium, pisiform, and
what’s the bonyfigure in your hand?
Probably lunate?Oh no, hamate, hook of hamate. Okay. Something
like the flexor retinaculum, you need to knowthe attachments because it’s quite an important
thing in the exam. This is your flexor retinaculum.
15:14
The proximal part of your flexor retinaculum
is your distal wrist crease. If you see yourdistal wrist crease in your hand, that is
the proximal part of the retinaculum.
15:24
Then if you ask a patient to extend the thumb fully,
extend it fully, then the ulnar border ofthe thumb forms the distal part of the retinaculum.
You extend it fully then identify the ulnarborder of the thumb. That’s your distal part
of the retinaculum. So this is your retinaculum.
15:46
The attachment here is the tubercle of the
scaphoid. Just remember that the carpal bonesare in a concave shape such that the retinaculum
does not attach to the entire bone. It justattach to specific points. So on the scaphoid,
it’s called the tubercle of the scaphoid.
16:08
Pisiform. The pisiform is a small bone so
it attaches to the pisiform. Here, it is ahook of the hamate, not the entire hamate,
hook of the hamate. And here, it’s a ridgeof the trapezium. So this is where the
attachment is.
16:26
So if you feel the bony prominence here, that
is your hook of hamate. Okay. Structures goingunder the retinaculum, this is very important.
So you have the median nerve then you havethe FDP and FDS to this finger, so eight of
them, and FPL. So ten structures. Ten structuresgo under the retinaculum, and what goes over
the retinaculum? Anyone? You know what, theflexor carpi ulnaris, what did you say, is
that radialis? No. You know, some of the booksdo say that but it’s not strictly accurate.
The flexor carpi radialis, does not gounder or over the retinaculum because it just
attaches to the base of the second metacarpal.
17:18
So it has nothing to do with the retinaculum.
Yeah, palmaris longus goes over the retinaculum.
17:24
What else? Ulnar nerve, ulnar artery, anything
else? If you have a patient coming with carpaltunnel, carpal tunnel syndrome, what is
it classically feature? They’ll have tinglingand numbness in the lateral three digits,
right? If you test for sensation, can that beaffected? It can be. But what about sensation
here, can it be affected? No. Why not?Radial nerve.
No. Here. It’s a branch.
18:04
Once it comes up before the --
That’s right. Okay. So, that’s the mediannerve. Approximately five centimeters before
the wrist crease, there is a branch calledthe palmar cutaneous branch of the median
nerve, which supplies the thenar eminence.
18:28
So if we have a patient with carpal tunnel,
because this is running over the retinaculum,that area is spared. How it work? After you
operate and see them postoperatively, youneed to test this because if that is lost,
then you have iatrogenically damaged the palmarcutaneous branch. Okay. What is radialartery? The radial artery comes here just
lateral to your FCR tendon. The deep branchgoes to the snuffbox, and then it comes out
through the thenar eminence to form the palmararch. But you have a superficial branch
which goes over the retinaculum, and anastomosiswith the ulnar artery and other side to form
the other part of the palmar arch. Essentially,you have a superficial branch of the radial
artery, palmar cutaneous branch of the mediannerve, palmaris longus, ulnar nerve, ulnar
artery. So these are all structures goingover the retinaculum. Okay. So, we have covered
the entire upperlimb on this. Couple of nerves we haven’t
covered, one is the long thoracic nerve whichcomes from C5, C6, and C7. So, root value
is C5, C6, C7. It lies in the midaxillaryline in the chest or the thorax, and it can
be damaged when you put in a chest drain ordo any surgery in the axillary region. So
that’s the long thoracic. Then a coupleof more nerves just for completion, we have
the nerve to subclavius from there and thenerve to rhomboid. But I don’t think you
need to know for the part A, you just needto -- if at all you’re asked, you just need
to get in your head that it has nothing todo with the cords. It is just an isolated
nerve coming off the root, nerve to subclaviusand the nerve to rhomboid. Okay. I think
that pretty much covers everything.
20:40
We are spot on time. What I’m going to do
is go through the slides. As I said, all theseslides are going to be available for you online.
So you don’t have to worry. The purposeof going to the slides is just to reinforce
what you have learned and for you to justhave a quick revision. Okay. I’ll come to
the axillary artery whenwe do the thorax and axilla as well. The shoulder
joint, a lot of theory. I haven't cover

About the Lecture

The lecture Nerve Injuries by Stuart Enoch, PhD is from the course Musculoskeletal - Upper Limb.

Author of lecture Nerve Injuries

Stuart Enoch, PhD

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Great lectures!

By Katalin J. on 09. April 2018 for Nerve Injuries

Loved these lectures. The ONLY thing that bothered me was that the heads of the audience kept blocking exactly the subject's hand during the demonstration. Other than that, great job!

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Great lectures!

By Katalin J. on 09. April 2018 for Nerve Injuries

Loved these lectures. The ONLY thing that bothered me was that the heads of the audience kept blocking exactly the subject's hand during the demonstration. Other than that, great job!

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